This application is related to and claims priority from Japanese Patent application No. 2002-250349 filed on Aug. 29, 2002, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a refrigerant cycle, for example, used for an air conditioner of a vehicle or an electric water heater. More particularly, the present invention relates to a refrigerant cycle including an ejector having a throttle changeable nozzle.
2. Description of Related Art
FIG. 7 shows a conventional ejector cycle (refrigerant cycle) described in JP-A-11-37577. The ejector cycle includes a compressor 101, a gas cooler 102, an ejector 103 and a gas-liquid separator 104, which are circularly connected. Moreover, the ejector cycle has a fixed throttle 105 serving as a decompressing device, and an evaporator 106 in a bypass passage. In the bypass passage, liquid refrigerant separated by the gas-liquid separator 104 flows into a low pressure refrigerant inlet 109 of the ejector 103 through the fixed throttle 105 and the evaporator 106. The ejector 103 includes a throttle unchangeable nozzle 107 having a fixed throttle that is unchangeable irrespective of a circulating amount of refrigerant in the ejector cycle. When the ejector cycle is, for example, employed for an air conditioner of an automobile, the air conditioner may be used to cool a passenger compartment with a high load in summer, and may be used to dehumidify the passenger compartment with a low load in winter. That is, the ejector cycle is required to be used under various use conditions. Accordingly, the throttle unchangeable nozzle 107 of the ejector 103 cannot deal with various loads caused by the various use conditions.
FIG. 8 shows an ejector 110, which has a changeable nozzle 112 and is described in JP-A-5-312421. The changeable nozzle 112 has a needle valve 111, which can control a throttle opening degree (exit opening dimension) of the throttle changeable nozzle 112. However, when an ejector cycle having the throttle changeable nozzle 112 is made so as to be able to deal with the various loads, the stroke range of the needle valve 111 is required to be larger. Accordingly, a valve control system for controlling the needle valve 111 is required to be larger.
In view of foregoing problems, it is an objective of the present invention to provide a refrigerant cycle with an ejector having a throttle changeable nozzle, which has a reduced size. It is another objective of the present invention to provide a refrigerant cycle with an ejector including a throttle changeable nozzle in which a throttle opening degree is suitably changed in accordance with a load change while the size of the ejector can be reduced.
According to the present invention, a refrigerant cycle includes a gas-liquid separator for separating refrigerant into gas refrigerant and liquid refrigerant, an evaporator in which the liquid refrigerant flowing from the gas-liquid separator is evaporated after being decompressed, a compressor for compressing the gas refrigerant from the gas-liquid separator, a radiator which cools the refrigerant discharged from the compressor, an ejector and a throttle control system. The ejector includes a high-pressure refrigerant inlet port from which refrigerant from the radiator is introduced, a low-pressure refrigerant inlet port from which refrigerant from the evaporator is sucked, a nozzle for decompressing refrigerant introduced from the high-pressure refrigerant inlet port, and a pressure-increasing portion in which refrigerant from the evaporator is sucked through the low-pressure refrigerant inlet port by a flow of refrigerant jetted from the nozzle and is mixed with the refrigerant jetted from the nozzle. The pressure-increasing portion of the ejector has a refrigerant outlet from which refrigerant is discharged to the gas-liquid separator. In the refrigerant cycle, the throttle control system includes a bypass passage diverged from a refrigerant passage at a diverging point that is upstream from the high-pressure refrigerant inlet port and being joined to the refrigerant passage at a join point that is downstream from the diverging point, a control valve for controlling a pressure of the refrigerant flowing through the bypass passage, and a pilot valve that controls of a throttle opening degree of the nozzle in accordance with a pressure difference between the refrigerant in the bypass passage and the refrigerant in the high-pressure refrigerant inlet port of the ejector. Accordingly, the throttle opening degree of the nozzle can be controlled in accordance with a load change such as a variation in the high-pressure refrigerant pressure or the high-pressure refrigerant temperature in the refrigerant cycle. The control valve controls the pressure of the refrigerant in the bypass passage in accordance with the load change of the refrigerant cycle, and the throttle opening degree of the nozzle is controlled by the pilot valve in accordance with the pressure. Therefore, in throttle control system, a large stroke mechanism of the control valve is not required. Therefore, the size of the throttle control system can be reduced.
Preferably, the throttle control system further includes a fixed valve that is disposed in the bypass passage to generate a middle pressure refrigerant by using a pressure difference between refrigerant upstream from the fixed value and refrigerant downstream from the fixed valve, and the pilot valve controls of the throttle opening degree of the nozzle in accordance with a pressure difference between the middle pressure refrigerant in the bypass passage and the refrigerant in the high-pressure refrigerant inlet port of the ejector. In this case, the fixed valve can be disposed in the bypass passage upstream from the control valve or downstream from the control valve. For example, the diverging point of the bypass passage is provided in a high-pressure refrigerant passage through which the high-pressure refrigerant inlet port of the ejector is connected to an outlet of the radiator. On the other hand, the join point of the bypass passage is provided in a low-pressure refrigerant passage. For example, the low-pressure refrigerant passage is a passage for connecting the low-pressure refrigerant inlet port of the ejector and an outlet of the evaporator, a passage for connecting a liquid refrigerant outlet of the gas-liquid separator and an inlet of the evaporator, or a passage for connecting the outlet of the pressure increasing portion and an inlet of the gas-liquid separator.
On the other hand, a pressure regulating member is disposed in the throttle control system upstream from the high-pressure refrigerant inlet port of the ejector to generate a middle pressure refrigerant in the bypass passage, having a pressure between the pressure of the refrigerant upstream from the pressure regulating member and the pressure of the refrigerant downstream from the pressure regulating member. In this case, the pilot valve controls the throttle opening degree of the nozzle in accordance with the pressure difference between the middle pressure refrigerant in the bypass passage and the refrigerant pressure in the high-pressure refrigerant inlet port. For example, the pressure regulating member is a valve that keeps the pressure difference at a predetermined fixed value.